In order for a gas utility to know a passage volume of a gas consumed by a customer, the gas utility arranges a gas meter at a demand place to charge fees based on the passage volume of the gas, which is measured by the gas meter. In this case, when the gas supplied to the demand place has a constant heating value per unit volume, a passage heating value of the gas that has passed through the gas meter, that is, a gross heating value of the gas consumed by the customer can be accurately derived based on the passage volume of the gas. Therefore, the fees can be appropriately charged.
However, gases having different heating values, which vary depending on time and location may be supplied to the demand place. In such a case, it is difficult for a related-art gas meter configured to measure only the passage volume of the gas to accurately derive the passage heating value based on the passage volume of the gas, and fees may not be appropriately charged.
In view of this, there has been proposed a gas meter configured to measure a temperature and a sound velocity of the gas, estimate the heating value in a standard state of the gas based on the measured temperature and sound velocity, and derive the passage heating value based on the estimated heating value in the standard state, the passage volume of the gas, and the temperature of the gas (for example, Patent Literature 1).